1. Field of the Invention
The invention relates to new anticalculus agents, dentifrice compositions containing these agents and use of these compositions to control calculus accumulation on teeth.
2. Related Art
Calculus is a hard, mineralized deposit which forms around teeth. This formation arises from deposition of crystals of calcium phosphate in the pellicle and the extracellular matrix of dental plaque. Various forms of calcium phosphate have been identified but the most difficult to remove and thermodynamically most stable form is called hydroxyapatite (HAP). Amorphous forms of calcium phosphate are believed to be the precursors of HAP. Regular brushing can usually remove the amorphous forms but is not fully effective to dislodge the final stable calculus form. Therefore it is desirable to prevent amorphous forms of calcium phosphate from transforming into HAP. The art has recognized that agents which interfere with the formation of HAP crystallization will be effective anticalculus agents.
Soluble inorganic pyrophosphate salts have over the last few years set the commercial standard as calculus or tartar control agents. This technology has been reported by Parran, Jr. et al. in a series of patents including U.S. Pat. No. 4,590,066, U.S. Pat. No. 4,515,772 and U.S. Pat. No. 4,684,518.
Anionic polymers, especially carboxylate group functionalized polymers, have been widely reported as effective against calculus. Typically, low molecular weight anionic materials of high charge density are preferred in most of the prior art. For example, U.S. Pat. No. 4,661,341 (Benedict et al.) discloses the use of low molecular weight polyacrylic acids (MW range 3500 to 7500) in dental compositions. U.S. Pat. No. 3,429,963 (Shedlovsky) teaches use of maleate-containing copolymers and vinyl sulfonates in toothpaste. U.S. Pat. No. 4,183,914 (Gaffar et al.) reports use of polymaleates as anticalculus agents. The materials of Gaffar et al. cannot be obtained above molecular weight 1,000 and often have low purity in available commercial samples. High levels of impurities result in polymeric materials of poor appearance, taste and inadequate safety.
Commercially most significant has been the use of synthetic, linear anionic polymers of higher molecular weight in combination with the inorganic pyrophosphates. This technology derives from work done by Gaffar et al. reported in a series of patents including U.S. Pat. No. 4,627,977, U.S. Pat. No. 4,806,340, U.S. Pat. No. 4,806,342, U.S. Pat. No. 4,808,400 and U.S. Pat. No. 4,808,401. Anionic polymers described therein were found to inhibit the action of pyrophosphatases in the mouth and thereby allow greater efficacy of the inorganic pyrophosphate. The commercially operative polymer is a methyl vinyl ether/maleic anhydride copolymer, available under the GAF trademark Gantrez.
Organic phosphonic acid derivatives, some in polymeric form, have been disclosed in U.S. Pat. No. 3,934,002 (Haefele). U.S. Pat. No. 4,892,724 (Amjad) cites a tartar inhibiting oral composition that includes a fluoride source, a dental abrasive, a carboxylate polymer and various phosphonic acids and their derivatives. A phosphated acrylic acid/hydroxyethyl methacrylate/alkyl methacrylic acid ester copolymer has been suggested in GB 2 139 635B (Causton) as useful in an oral composition for treating teeth. U.S. Pat. No. 4,892,725 (Amjad) reports a fluoride oral composition with an anticalculus agent that includes a first polymer selected from homopolymers of carboxyl monomers and a second polymer which is a copolymer containing at least 30% of the carboxyl monomer. Related to this disclosure is U.S. Pat. No. 4,842,847 (Amjad) focusing upon a fluoride containing oral composition having an anticalculus agent selected from homo and copolymers, the latter containing at least 30% by weight of monocarboxylic or dicarboxylic monomer units. Combinations of polyacrylic acid derivatives, strontium and fluoride ion sources along with a soluble pyrophosphate have been reported in U.S. Pat. No. 4,847,070 (Pyrz et al.).
Evident from the foregoing review of the art is the considerable effort expended to devise better calculus control compositions. By no means, however, has any of the reported art been able to more than attenuate the problem. There is considerable room for improvement over the known control agents.
Accordingly, it is an object of the present invention to provide a material of improved efficacy in controlling formation of calculus.
A still further object of the present invention is to provide a tartar control agent of improved taste, safety and appearance.
These and other objects of the present invention will become more apparent in light of the detailed description and Examples which follow.